A cathode for lithium-sulfur battery has typically been manufactured by preparing a slurry in which a conducting material, an active material, a binder, and a solvent are mixed together and subsequently coating the slurry on a metal current collector.
Since typical cathode for lithium-sulfur battery has been manufactured through a precise and qualitative coating process, and contacts between conducting materials and between a conducting material and an active material may be well made. However, after manufacturing a cell, the cathode is repeatedly charged and discharged during operation, and thus, the active material may be changed. Further, due to partial loss of the active material, charge/discharge efficiency and energy efficiency may be reduced and life of the cell may also be reduced.
In order to solve such a problem, in the related arts, a technique in which sulfur, a binder, a conducting material, and a solvent are mixed in the form of slurry to manufacture a cathode for lithium-sulfur battery and then casted and dried on a metal collector has been developed to provide the electrode. However, in both of a wet method using a solvent and a dry method without using a solvent, the technique has a problem that sulfur and a conducting material may not been mixed sufficiently to have an even contact area. In particular, it has been recently reported that a cathode structure including an active material and a conducting material in a uniform manner may be loosely maintained and the initial equilibrium state may be rapidly collapsed after charge and discharge, thereby causing reduction in life span of the lithium-sulfur battery (Journal of The Electrochemical Society, 159 (8) A1226-A1229 (2012)). For example, in a cathode structure of a lithium-sulfur battery, a uniform structure in the initial state including an active material and a conducting material uniformly mixed with each other may be collapsed by repeated charge and discharge, and thus, sulfur may be eluted, thereby causing a remarkable decrease in charge/discharge capacity.
Further, in the related arts, a cathode for lithium-sulfur battery obtained by coating cathode active material slurry on a porous current collector manufactured from carbon fiber has been provided. Moreover, a method for accommodating a sulfur electrode active material within a fiber conductor by spraying a solution containing a carbon nanotube on the fiber conductor using carbon felt has been developed.
Furthermore, an electrode structure for battery has been provided. The electrode structure may include porous supporter formed of elongated fiber and contain sulfur as an active material, and pores of the porous supporter may be partially coated with a conductive material. Alternatively, a sodium-sulfur battery having a structure in which sulfur (S) as a cathode active material is impregnated in a mat formed of carbon fiber fabrics has been developed.
However, although the techniques in the related arts as described above have made some progress in improving charge/discharge efficiency or capacity by suggesting the technique for accommodating an active material within a porous current collector or supporter or a conductor in an electrode for battery, performance of the active material has not yet been fully maximized. For example, leakage of the active material to the outside of the supporter or the conductor may result in loss of the active material or a decrease in stability of conductivity.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.